Since the late 1980s ... most originalists have shifted [from "original intent"] to the “original public meaning” camp, which argues that the Constitution should be interpreted as it would be understood by readers of the text at the time it was ratified. Original meaning originalists disagree about exactly whose understanding of the text is relevant. Some emphasize the understanding held by legally sophisticated readers, such as judges, lawyers, and legal scholars. Others focus on the understanding of a hypothetical “reasonable” reader of English at the time, who may or may not be legally sophisticated, depending on the views of the theorist in question.

Upham’s evidence is very powerful from the standpoint of theories of original meaning that emphasize the understanding of actual or hypothetical readers expert in law. Most of his evidence consists of the views of just such experts, particularly those associated with the political movement that supported the Amendment. But many original meaning theorists emphasize not the understanding of experts, but that of the general public—either the actual public or a hypothetical non-expert “reasonable” reader at the time. After all, ratification is ultimately supposed to be a democratic process that expresses the will of the people, not just a small elite.

It is far from clear that ordinary citizens shared the understanding advocated by Republican elites in the 1860s and 1870s. The text of the Amendment does not unequivocally state that laws banning interracial marriage are now unconstitutional. The average reader of English would not readily understand that a provision barring states from “abridge[ing] the privileges or immunities of citizens of the United States” would necessarily require them to permit interracial marriage. And there is little doubt that most whites, in both the North and the South, strongly disapproved of interracial marriage, as they continued to do until late in the twentieth century. Had a majority of the general public believed that the Fourteenth Amendment would require state recognition of interracial marriages between blacks and whites, opposition to the Amendment would likely have been much stronger, and it might not have been ratified. Upham does cite a few newspaper articles suggesting that popular support for interracial marriage was rising in the 1860s and early 1870s. But more evidence would be needed to show that such support had advanced to the point where anything like a majority of voters believed that the Fourteenth Amendment had banned antimiscegenation laws.

I agree this is an important methodological issue, but I think (particularly in this case) the right approach is clear. Words get meaning from their context. The context of words in a constitution, statute, treaty, etc., is that they are part of a legal document. In a legal document, one would expect to encounter a legal vocabulary. Thus the right way to understand words in a legal document -- whether you are a member of the legal community or an ordinary non-legal person -- is to understand those words' legal meaning.

This approach is not something unique to law: if I -- a lawyer, not a doctor or an engineer -- am reading a medical document or an engineering document, I am going to try to find out the medical or engineering context of the words in the document, not try to work out what the words (shorn of their context) mean to me at first sight. Or at least, that's what I should do.

This approach is particularly sensible when the words in question do not have an obvious non-legal meaning. To take Professor Upham's subject, "privileges or immunities of citizens" does not have a common meaning apart from its legal context. To the extent it has any specific meaning, that meaning must come from the way the phrase was understood in the legal vocabulary.

As a result, I think that regardless of whether the objective is the original legal meaning or the meaning to a well-informed ordinary reader of the time, the answer is the same. An ordinary well-informed reader would seek out the legal meaning, because that it is the best way to understand words in a legal text.

As Professor Somin says, though, that may not be what ordinary people of the time actually understood, because many ordinary people may not have taken time to inform themselves of the best meaning of the legal text. I think that possibility does not call for a different interpretive approach, however, for at least two reasons. First, it seems a hopeless task to assess what ordinary people actually understood, without using as a proxy the text's legal meaning. Second, especially for constitutional text, the legal meaning likely is a fair proxy for what many ordinary people understood. Because a constitutional text has to be ratified (indirectly, in this case) by ordinary people, if its legal meaning is something ordinary people might oppose, its opponents have a very strong incentive to educate ordinary people about its legal meaning.

As a result, I'm less concerned about the possible divergence between legal meaning and ordinary understanding, especially in the case of the Professor Upham's subject. I agree, though, that it would be troubling if there was evidence of a wide gap between the original common understanding of the text and the text's original legal meaning.